1. Field of the Invention
This invention relates generally to remote automatic meter reading and control systems and more particularly to a meter terminal unit or transponder for use in such systems to effect the carrying out of meter reading and load control operations at terminal points along a communication line such as a utility power transmission network.
2. Description of the Prior Art
Utility companies have long used meter reading personnel for reading the consumed commodity information provided by utility meters (i.c. gas, water, electricity, and the like). However, in recent years significant strides have been made in the development of fully automatic meter reading systems.
Most remote meter reading systems have similarities in their designs. Generally, they comprise some type of encoder device attached to a meter to give an indication of the meter reading, means for storing the meter reading indicated and a transponder for transmitting meter data over a communication link to a central station or control center when interrogated by a signal from the central station. One known system utilizes a mobile van which travels over a specified route in a community and, while traveling, transmits interrogate signals to meter equipment transponders at the houses located along the traveled route. The transponder at each house, in response to the interrogating signals, transmits a message to the van which includes a meter identification number and the present reading of the meter. Receiver equipment in the van effects the storage of the meter data for subsequent use in billing the customer.
Various other types of systems have been developed which utilize the telephone lines of the subscriber as the communication link to the central station. Also, there are arrangements in which the power lines of the subscriber and the utility company are used as the link between the customer's meter and the central station.
While many communication systems have been developed for utility companies, all of which utilize one or more of the various links and equipment aforementioned, no known economical feasible meter terminal unit or transponder has yet been designed for use in such systems which affords the capabilities of mass meter data accumulation and load control at a consumer residence and which meets the universal needs of utility companies.
An electric power network, involving as it does a vast number of meter locations, logically dictates that the most economical communication system will be that system which affords a minimum expenditure for the transponder equipment at each meter location, while allowing a greater expenditure for more sophisticated equipment for the processing of large amounts of meter data and the rapid distribution of command information to the transponder meter locations. This logical consideration has generally made the approach of providing radio receiver transmitter units at each meter location unfeasible. In effect this approach involves the use of as many communication systems as there are meter terminal locations. The desired approach, by contrast, would utilize an existing communication network which links all meter terminal locations together and would minimize the expense of the control equipment at each terminal location. Further, overall system control would be effected by a control station and section or group equipment which being required in smaller numbers can be of greater sophistication.
Additionally, the desired system would allow utility companies to read all meters in a city at desired intervals, such as during daily peak power periods. This has the advantage of allowing the utility companies to improve the system load factor by encouraging the customer to improve his residential load factor. This improvement of load factor can be accomplished in a number of ways by effecting a shifting of loads on the system from on-peak periods to off-peak periods. Three modes, but not necessarily all inclusive, of accomplishing this load-shift have been suggested as follows:
1. Alerting the customer by the automatic activation of an indicator at his residence via a meter terminal unit when he is using energy during peak periods so that he can reduce his load during those periods. PA1 2. Metering and billing the customer at a premium rate for his on-peak usage as determined from stored meter data collected from the customer's meter terminal unit. PA1 3. Controlling or limiting the customer's on-peak usage of energy by automatically turning off various loads in his residence (e.g. hot water heaters, clothes dryer, etc.) via a meter terminal unit during those periods.
Thus, it can be seen that a need exists for an improved meter terminal unit for use in an automatic meter reading and control system which affords the preceding advantages and which has a built-in flexibility to accomodate future changes in utility company operating philosophy.
The system disclosed herewin, which makes use of the present invention, is also disclosed and claimed in U.S. patent application, Ser. No. 653,859 filed Jan. 30, 1976, now U.S. Pat. No. 4,135,181 entitled "Automatic Remote Meter Reading and Control System" and is assigned to the same assignee as the present invention.